Fix test failure caused by new trace stats field

BUG=991282

Change-Id: I7b815ed53acdec98ca7e8b1d50c92d92414988b3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1740330
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Reviewed-by: oysteine <oysteine@chromium.org>
Commit-Queue: ssid <ssid@chromium.org>
Commit-Queue: oysteine <oysteine@chromium.org>
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Cr-Commit-Position: refs/heads/master@{#684571}